1. Field of the Invention
The present invention relates to network devices, and more particularly to a network device for building virtual networks.
2. Description of the Related Art
In network management, system administrators need to understand how the network is laid out. To identify the topology of a network, they use Packet Internet Grouper (ping) commands from a terminal console (e.g., personal computer) attached to the network. A ping command verifies end-to-end connectivity to a specified destination.
Topology discovery can also be achieved by using a dedicated network monitoring tool or a computer with equivalent software functions. Examples are seen in Japanese Patent Application Publications No. 10-93635 (1998) and No. 2003-115843.
Virtual local area network (VLAN) technology enables a single physical network to be logically segmented into multiple networks. A network design tool proposed in Japanese Patent Application Publication No. 2004-40374 permits a network engineer to view the structure of a physical network and VLAN segments in an associated manner. This tool makes it easy to design and maintain a VLAN environment.
In real-world implementations, a large network accommodates several tens to several hundreds of VLAN domains mapped on a single physical network. The existing management tools such as those proposed in the aforementioned publications are unable to offer the capability of VLAN topology discovery per se. There has been an unfulfilled demand for devices that can discover the topology of a network system including many VLAN segments.